The term “brine” means herein a concentrated saline solution of sodium chloride and other salts. Concentrated solution that do not contain sodium chloride are not called herein “brines”, although they are so called at times in the literature. The Dead Sea End Brine hereinafter briefly indicated by “EB”) is the brine that remains after the final concentration stage in the process for the production of carnallite from Dead Sea waters. It contains 20-27 wt % Cl−, 0.75-0.95 wt % Br−, 2-5 wt % Ca++ and 5-7 wt % Mg++. Any solution of the above salts, having salts concentration substantially within the above limits, is a brine comprised in this application, regardless of its origin, and what is said hereinafter about EB should be understood as applying to any solution having salts concentration substantially within the above limits. Calcium bromide solutions, having concentrations e.g. close to 50 wt %, are used as clear drilling fluids and optionally may be used as bromine carriers. CaBr2 is presently prepared by direct reaction of liquid solution of HBr with Ca(OH)2 (lime) or CaCO3, followed by filtration and concentration. This process, however, is expensive, particularly because hydrobromic acid must be made from bromine, which is produced from the same EB by stripping with chlorine.
It would be desirable to avoid these chemical processes and to recover calcium bromide directly from brines which contain it, and this is one of the purposes of this invention.
Extraction processes are known in the art. Robert R. Grinstead et al. describe the recovery of magnesium chloride from sea water concentrates in the article “Extraction by Phase Separation with Mixed Ionic Solvents” in Ind. Eng. Chem. Prod. Res. Develop., 9, No. 1, March 1970. This article describes how magnesium chloride is reversibly extracted from an aqueous feed brine, which is a sea water concentrate, by an organic phase, and is subsequently stripped from the organic phase by contact with water to produce a magnesium chloride solution. The organic phase used was a solution of a quaternary amine (Aliquat 336) and naphthenic acid or of a primary amine (Primene JMT) and naphthenic acid, in toluene. Although calcium is present in sea water, little calcium ion is normally found in solution in said concentrates, because of the substantial sulfate concentration, and accordingly, it was not considered in the said article. The separation considered was mainly of MgCl2 from NaCl.
The equipment described by Grinstead et al. consists of an extractor having a number of stages and a stripper having another number of stages. The feed brine is loaded into the extractor, the loaded organic phase is loaded into the stripper. Water is fed to the stripper, from which a product brine is obtained. The organic phase, stripped in the stripper, is returned to the extractor. The final product solution is obtained from the stripper.
C. Hanson et al., in Proceedings International Solvent Extraction Conference 1974, Vol. 1, p. 779-790, have described a process for the recovery of magnesium chloride from sea water concentrates using a mixed ionic extractant. Several systems of ionic extractants have been studied by the authors, and the best results are said to be obtained with an equimolar mixture of Aliquat-336 and Acid-810. Aliquat-336 is a mixture of quaternary alkyl ammonium chlorides and Acid-810 is essentially a mixture of isooctanoic, isononanoic and isodecanoic acids. Toluene was found to be a satisfactory diluent.
C. Hanson et al., in “Extraction of Magnesium Chloride from Brines Using Mixed Ionic Extractants”, J. Inorg. Nucl. Chem. 1975, Vol. 37, p. 191-198, describe the use of organic extractants, using as amines Alamine-336 (mixture of tertiary amines), Aliquat-336 (mixture of quaternary amines), Amberlite LA-2 (mixture of secondary amines) and Primene JM-T (mixture of isomeric primary amines), and using carboxylic acids as Acid-810, naphthenic acid and Versatic acid 911. The diluent used was toluene.
U.S. Pat. No. 3,649,219 describes a process for extracting inorganic salts from aqueous solutions which comprises contacting the aqueous solution with an extractant liquid, which comprises an acid member and a base member, which is an amine, separating the resulting inorganic-salt-containing extractant liquid from the inorganic salt depleted aqueous phase, and stripping the inorganic salt from the extractant liquid by water.
The prior art deals mainly with separation of MgCl2 from NaCl. The data about the extraction of calcium salts are limited and include mainly chlorides. There are no data on the separation of two salts of divalent metals. This invention applies to an even more complicated system, dealing with the separation of four salts of divalent metals: CaBr2, CaCl2, MgBr2 and MgCl2. Furthermore, the references actually describe laboratory experiments and not an industrially valid process, and do not take into consideration the problems which arise in industrial operation.
It is therefore a purpose of this invention to provide an industrial process for producing calcium bromide by extraction from brines that contain it, particularly Dead Sea End Brine.
It is a further purpose of this invention to provide such a process which permits to extract calcium bromide in high yields.
It is a still further purpose of this invention to solve the various problems which are encountered in the extraction of calcium bromide from EB and other brines, which will be specifically detailed hereinafter.
Other purposes and advantages of the invention will appear as the description proceeds.